Many different chair designs are known in practice. In the so-called three-point mechanism, the seat, the base support and the backrest are coupled together via three articulation points in such a way that a predetermined synchronous relationship is established between the inclination of the seat and the inclination of the backrest. With respect to the location of the pivot point, three-point mechanisms of this type represent a compromise between different ergonomic requirements, which cannot be satisfied independently of one another.
DE-B-103 18 759 describes a two-point mechanism in which the seat is pivotably mounted on the base support with the interposition of a spring system. Furthermore, means are provided for adapting the spring behavior of this spring member to different requirements. The backrest is connected to the seat via an articulation axis, wherein synchronization between the inclination of the seat and the inclination of the backrest is rendered possible by means of a cable construction provided between the base support, the seat and the backrest.
A chair which has a two-point mechanism is known from DE-A-43 31 987, wherein the seat is pivotably mounted on the base support and the backrest is pivotably mounted on the seat, and a first spring system is provided between the base support and the seat and a second spring system is provided between the seat and the backrest. The special feature of this chair consists in that the pivoting axis of the seat is provided in the region of the user's ankles, and the pivoting axis of the backrest extends at least approximately through his hip joints. In this arrangement, the pivoting movement of the backrest in relation to the seat is not mechanically coupled to the pivoting movement of the seat in relation to the base support.
The object of the invention is to develop the chair further so that it can be adapted in a simple manner to different requirements, especially to users of different weights.